title: Torque modulates nucleosome stability and facilitates H2A/H2B dimer loss.
abstract: The nucleosome, the fundamental packing unit of chromatin, has a distinct chirality: 147 bp of DNA are wrapped around the core histones in a left-handed, negative superhelix. It has been suggested that this chirality has functional significance, particularly in the context of the cellular processes that generate DNA supercoiling, such as transcription and replication. However, the impact of torsion on nucleosome structure and stability is largely unknown. Here we perform a detailed investigation of single nucleosome behaviour on the high-affinity 601-positioning sequence under tension and torque using the angular optical trapping technique. We find that torque has only a moderate effect on nucleosome unwrapping. In contrast, we observe a dramatic loss of H2A/H2B dimers on nucleosome disruption under positive torque, whereas (H3/H4)₂ tetramers are efficiently retained irrespective of torsion. These data indicate that torque could regulate histone exchange during transcription and replication.
authors.affiliation: Department of Physics-Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Maxim Y
authors.initials: MY
authors.lastname: Sheinin
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Mohammad
authors.initials: M
authors.lastname: Soltani
authors.forename: Karolin
authors.initials: K
authors.lastname: Luger
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Wang
mesh_terms: D000818:Animals; D004247:DNA / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D006367:HeLa Cells; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry* / Q000378:metabolism; D052898:Optical Tweezers; D055503:Protein Multimerization; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D019415:Torque; D014158:Transcription, Genetic; D014982:Xenopus laevis / Q000235:genetics
chemical_list: D006657:Histones; D009707:Nucleosomes; D004247:DNA; D012319:RNA Polymerase II